There are many circumstances where rotary mechanical power from a totally self-contained unit is highly desirable, e.g., to power an artesian pump in a remote desert location where the only source of energy is the sun. The engine should operate over a long period of time without the need for any external source of electricity or manual inputs to restart it after a stop or to control its operation between stops. It is also absolutely essential that the engine when provided with working fluid vapor at a predetermined condition, has the capacity for starting automatically, operating satisfactorily thereafter, ceasing operation when working fluid vapor is no longer available at the predetermined condition, and stopping in readiness for the next automatic restart--all without human intervention except for repair or scheduled maintenance.
Conventional closed loop solar collector systems typically are designed to include one or more electrically-operated servo-type valves to control engine vapor intake and to regulate the output of the engine to maximize operational efficiency. Such controls, however, require an external source of electrical power and are not particularly suitable for unattended operation over prolonged periods of time in remote areas. Likewise, it is preferable to eliminate the need for manual controls. Furthermore, it is highly desirable to completely seal-in the operating components of the engine to preclude contamination by dirt, moisture and other ambient pollutants and to maintain within the engine a subatmospheric pressure or vacuum for higher operational efficiency.
In my earlier issued U.S. Pat. No. 4,698,973, titled "CLOSED LOOP SOLAR COLLECTOR SYSTEM POWERING A SELF-STARTING UNIFLOW ENGINE", issued on Oct. 13, 1987 and incorporated herein by reference, there is disclosed and claimed a closed loop solar collector system that receives collected solar energy to vaporize a working fluid for delivery to a single piston uniflow system. The disclosed engine includes a single piston capable of acting directly upon a pair of normally closed intake valves projecting into the engine cylinder to actuate the same. Under relatively low pressure conditions in the boiler or vaporizing unit, a spring-loaded connecting rod facilitates control of the engine so that, in principle, the engine has the ability to start when available working fluid vapor attains a predetermined pressure and, thereafter, changing over from a start-up mode to a normal running mode of operation when the rotational speed of the engine attains a predetermined mode-change value. It is believed, however, that a single piston reciprocating in a single long cylinder could possibly come to a stop in an end-of-stroke position that may frustrate a subsequent restart. In other words, to promote wide use of uniflow engines with closed loop solar powered systems, it is believed necessary to have a sealed-in engine that will always start when working fluid vapor is delivered at a certain minimum pressure regardless of the engine crankshaft position when it comes to a stop.
The present invention, therefore, provides a multicylinder uniflow engine designed to restart readily no matter what position the crankshaft takes when the engine comes to a stop. The engine will always restart when working fluid vapor is available to the engine at a predetermined condition, e.g., when the static pressure of the working fluid vapor exceeds a predetermined value.
It should be appreciated that an engine of the type taught in this invention preferably should have as few mechanical moving parts as practical, be capable of completely sealed-in operation, and have a simple sturdy design, e.g., not be dependent on springs that may lose their elasticity or break over time, so that it will not require expensive or difficult production techniques or maintenance after installation.